With a development of information technology, mobile apparatuses miniaturized to be portable, such as cellular phones, MP3, laptop computers, PDAs, digital camcorders, digital cameras, etc., are receiving much attention from consumers. Digital convergence products which combine several functions lead the market of mobile apparatuses. Most cellular phones are combined with a digital camera module. Cellular phones in which digital camera modules are built as image photographing devices have been improved as greatly as enough to threaten the digital camera market. Recent cellular phones have high-resolution, compact digital camera modules that have several millions of pixels. Although being small, such high-resolution, compact digital camera modules need to be able to execute auto focusing or optical zooming in order to obtain a precise image.
More specifically, in a conventional image photographing device having a relatively small number of pixels, a lens group is fixed in a direction parallel to an optical axis to reduce the manufacturing costs or the size of the image photographing device. The focal point of the lens group is fixed at an initial position, such that when the lens group is out of focus, it is focused by artificially moving the image photographing device and adjusting the distance between the lens group and an object. The conventional image photographing device cannot achieve optical zooming because the lens group is fixed in the direction parallel to the optical axis. The conventional image photographing device controls a photographing magnification by using a digital zooming function in which an optical image captured by the lens group is converted into an electrical signal by an image sensor and the electrical signal is magnified. Recently, a demand for high-quality images increases according to an increase of the number of pixels to about several millions. Image photographing devices having driving mechanisms that can move the lens group in the direction parallel to the optical axis have appeared. Driving mechanisms are classified into piezo type driving mechanisms, linear motor type driving mechanisms, and voice coil type driving mechanisms according to the type of an actuator.
Although such automatic focus control or optical zooming is already popular in existing digital cameras, they are still difficult to be performed in compact digital camera modules whose width and length are reduced to several tens of mm or less. To make the automatic focus control or optical zooming be executed in compact digital cameras, the driving mechanisms need to be extremely improved.
Image photographing devices that perform automatic focus control and optical zooming generally include a lens group, a housing that forms the outer appearance of the image photographing devices, an actuator that moves the lens group in the direction parallel to an optical axis, and a support member that supports the lens group flexibly so is that the lens group can move in relation to the housing. Compact image photographing devices, which are installed in mobile apparatuses, should improve the portability by reducing their sizes and weights and increase the use time of battery by reducing power consumption. Accordingly, the lens group should be small and light, and the power consumed by the actuator should be minimized. The support member should have a minimal elastic coefficient to reduce the driving energy of a lens group having a predetermined size and weight while stably supporting the lens group. The support member is generally a metal plate spring or wire.
For example, an optical pickup device, which reads digital data from an optical disc, includes a lens that projecting a laser beam to the optical disk, a wire that supports the lens so that the lens moves in focusing and tracking directions, and a voice coil attached to a side surface of the lens to generate a driving force. The wire is formed of a conductive material, such as, stainless steel (SUS), yellow copper, or beryllium-copper (BE-CU) alloy. A terminal of the voice coil is soldered to the wire, and the wire is connected to a power unit. Power supplied by the power unit to the wire enters into the voice coil via the soldered portion and the terminal of the voice coil and generates an electromagnetic force required to drive the lens.
In conventional image photographing devices, a mechanism for supporting and driving the lens group which photographs an optical image is similar to that of the aforementioned optical pickup device. Accordingly, the support member of the conventional image photographing devices is formed of a metal and has a shape of a leaf spring or a wire. The leaf spring or the wire has a minimal thickness (e.g., 0.3 mm) to reduce an elastic coefficient. A process, such as, etching, is used to shape metal into a support member having a thickness of 0.3 mm or less. Hence, the yield of the support member is very low when considering the small sizes and thicknesses of the conventional image photographing devices.
When a force exceeding an elastic range is exerted on the metal used to form to the support member, the metal is plastic-deformed. In addition, the metal is prone to fatigue destruction by repetitive load. Suppose that the weight of the lens group, the thickness of the support member, and an electromagnetic force generated by the voice coil are predetermined, the support member should be able to maximize bending or twisting deformation to improve the position controllability along with the optical axis. Accordingly, the support member is designed to have a complicate shape to have various inflection points. The support member having the above-described material, size, and shape in the conventional image photographing devices is plastically deformed when an allowable external force or an excessive current is applied to the voice coil. When the support member is plastically deformed, the conventional image forming device cannot be anticipated to properly operate.
In addition, as the size of an image photographing device is reduced and the number of pixels increases, foreign materials entering the image photographing device degrade the quality of an image. In particular, foreign materials, such as, flux generated during soldering of various components, sensitively affect the quality of an image. There remains a demand for an assembly that can reduce foreign materials, such as, flux, entering an image photographing device.